Since you said "What is your opinion" Mine is that it is safe.
However, if you wish to pick nits.
The "Danger" is that you have a cord rated at 30 amps, but it's protected by a breaker rated at 50.. Now, in theory it is possible to create a "Short" that will draw say 40-45 amps, not quite just enough to pop the circuit breaker but enough to seriously overheat the wires in the cord.
In practice, outside of a lab, dang near impossible to create such a short.
IF there is a short INSIDE the RV, then the 30 amp main breaker in your distribution panel will trip, thus protecting the cord. (not to mention many other things) or the lower current affected branch breaker will trip.
Now,,,, Why do it?
Well, epically if you use an RV Surge Guard/Power line protection device.
The lower voltage drop in the 50 amp wires "Up-stream" of the surge guard may cause it to hang in there in some few parks. Where as on a 30 amp site, when the air conditioner cuts in, the power guardian may shut you off it it's a bit too fast to respond.
